The present invention relates to a focused ion beam processing apparatus for performing fine-processing on a sample surface by scanning and irradiating a focused ion beam onto the sample surface while injecting blowing a gas thereon.
In order to carry out selective etching, enhanced etching or deposition processing using a focused ion beam apparatus, processing is conducted while locally injecting blowing a gas to a focussed ion beam irradiating site.
Gases used for performing this etching (etching gas) include principally a halide-based gas to provide reactivity with a sample material, while gases used for performing deposition (deposition gas) include a carbonyl-based compound. Hereinafter, both etching assist gas and deposition assist gas will be collectively referred to herein as material gas.
In the above-described charged particle beam apparatus, when blowing a gas onto a sample, a sample chamber is also filled by the gas. Where the gas is incident on and precipitated on an ion beam optical system surface and a high voltage is applied to the ion optical system, discharge is likely to occur.
If discharge occurs during a process, a beam will impinge on for the sample portions than a predetermined irradiation area. Desired processing or observation can not be done. Also, the occurrence of discharge causes a large amount of current to flow to the ion optical system control unit, resulting in the possibility of damaging the control unit or the like.
In order to solve the above problem, a roughening liable to induce high voltage discharge is prevented from being formed which makes it difficult for gas to be adsorbed on the ion optical system surface and prevents it from precipitating thereon.
The mean adsorption time t that the gas is adsorbed on the ion optical system surface can be expressed as follows, wherein an activation energy for escape is expressed by the variable Ed.
t=T0 EXP(Ed/RT)
where t0 is a constant, R is a gas constant and T is absolute temperature.
In the above equation, when t approaches 0 endlessly, there becomes almost no gas adsorption on the ion optical system surface. Due to this, gas adsorption can be prevented from occurring by heating the ion optical system surface such that the mean adsorbtion time t decreases.
Also, the material gas to be used for ion beam processing is generally one that is high in vapor pressure. The substance not in vaporization at normal temperature is solid or liquid at normal temperature, which is vaporized by heating to be blown to a sample surface.
Due to this, if the gas contacts a part that is lower in surface temperature than a vaporizing temperature or a temperature at which no precipitation occurs under gas atmospheric pressure, there is a possibility of solidification or liquidization. In this case, adsorption can be shortened or precipitation can be prevented by conducting part heating to a temperature not lower than the temperature of vaporization or the temperature at which no precipitation occurs under the gas atmospheric pressure.